All U.S. patent cited herein are hereby fully incorporated by reference.
Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems commonly referred to as air bag systems have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9, 1996, the teachings of which are incorporated herein by reference.
Inflatable cushions for use in the protection of passengers against frontal or side impacts must generally have a more complex configuration since the position of a vehicle passenger may not be well defined and greater distance may exist between the passenger and the surface of the vehicle against which that passenger might be thrown in the event of a collision. Prior cushions for use in such environments are disclosed in U.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No. 5,454,594 to Krickl; U.S. Pat. No. 5,423,273 to Hawthorn et al.; U.S. Pat. No. 5,316,337 to Yamaji et al.; U.S. Pat. No. 5,310,216 to Wehner et al.; U.S. Pat. No. 5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 to Wallner et al.; U.S. Pat. No. 4,944,529 to Backhaus; and U.S. Pat. No. 3,792,873 to Buchner et al.
The majority of commercially used restraint cushions are formed of woven fabric materials utilizing multifilament synthetic yarns of materials such as polyester, nylon 6 or nylon 6,6 polymers. Representative fabrics for such use are disclosed in U.S. Pat. No. 4,921,735 to Bloch; U.S. Pat. No. 5,093,163 to Krummheuer et al.; U.S. Pat. No. 5,110,666 to Menzel et al.; U.S. Pat. No. 5,236,775 to Swoboda et al.; U.S. Pat. No. 5,277,230 to Sollars, Jr.; U.S. Pat. No. 5,356,680 to Krummheuer et al.; U.S. Pat. No. 5,477,890 to Krummheuer et al.; U.S. Pat. No. 5,508,073 to Krummheuer et al.; U.S. Pat. No. 5,503,197 to Bower et al.; and U.S. Pat. No. 5,704,402 to Bowen et al.
As will be appreciated, the permeability of the cushion structure is an important factor in determining the rate of inflation and subsequent rapid deflation following the impact event. In order to control the overall permeability of the cushion, it has generally been desirable to utilize certain coatings (such as silicones) to fill the interstitial space between the individual yarns in the airbag structure, as well as to attempt to keep such yarns from shifting (and thus create larger open spaces within the fabric) during an inflation event. Thus, it has been common to utilize relatively thick coatings, comprised of such materials as silicones, for example, to reduce the permeability of such airbag fabrics. The utilization of such coatings, however, has limited the availability of different woven fabric structures as the base airbag fabric.
In order to reduce the number and amount of interstitial spaces between fabric yarn s, the woven structure has necessarily been very dense (i.e., high picks per inch of fabric and high yarn denier). Fabric density is measured in general by what is termed a "cover factor." This factor measures the product of the number of warp yarns per inch of fabric and the square root of the denier of the warp yarn all added to the product of the number of weft yarns per inch of fabric and the square root of the denier of the weft yarn. A high cover factor fabric will therefore comprise relatively high denier yarns in both warp and weft directions, all woven to a high picks per inch count. In the past, the lowest airbag fabric cover factor utilized for within any airbag applications has measured about 2000 (210 denier yarns in both directions, 69 picks/inch and 69 ends/inch=1999.8 or roughly 2000). As noted above, since air permeability is of utmost concern within airbag applications, the use of such dense fabric has been necessary, in combination with standard airbag coatings, to provide such desired low air permeabilities. If the density of such fabric were any lower, the standard coatings would not properly coat the fabric surface; most likely the coating materials would leak through the fabric and not provide any real barrier to air. Also, without the utilization or presence of coating on the surface of low cover factor (low density) airbag fabrics, the air permeability would be much too high for such fabric to function properly. The low density fabric would possess to much potential open space between individual yarns to act as a barrier to air during an inflation event. Thus, there has been no disclosure or fair suggestion in the past or within the prior art of trying to incorporate low density (low cover factor) fabrics within airbag cushions. Although such weave structures could be highly cost-effective (due to a reduction in the need for specialized, difficult weaving procedures, and lower denier yarns), again, the prior art has not accorded any instruction or mention to the ordinarily skilled artisan regarding the possible or proper utilization of such low cover factor fabrics within airbag cushions.